There are three basic approaches for establishing criteria for manual materials handling (MMH) standards of guidelines. These are the Psychophysical, the Physiological, and the Biomechanical. These approaches have yielded data on lifting capacity which conflict. Therefore prior to the establishment of any guidelines or standards for MMH any conflicts must be resolved to determine a criterion or a set of criteria to be used for this purpose. In phase I, the proposed research is designed to achieve this end, namely, use both the physiological and psychophysical techniques to determine which of these should be used for establishing MMH guidelines or standards. The proposed work calls for three experiments using both operator and task variables to determine the capacity of lifting and develop models to predict this capacity. Both of these will be a function of the task and operator variables. The objectives of the proposed work are to determine whether or not a single criteria can be used for MMH standards, to establish the optimum weight/bulk ratio for containers, to determine the effects to spine twist on MMH capacity, to study the effects of training on MMH capacity, and to study the interactive effects of task variables on MMH capacity. During Phase II of the proposed work, it is planned to carry out an intervention study where results of the phase I work as well as previous research results will be implemented in a typical industrial environment. Thus phase II will investigate the effectiveness of job redesign as well as screeining techniques (for assigning personnel to jobs which are within their MMH capacities) in terms of MMH injury reduction in both frequency and severity.